The present invention relates to cigarette filters of shaped micro cavity fibers impregnated with flavorants that modify the flavor of a smoke stream during the smoking process.
Many types of tobacco smoke modifying agents such as menthol flavorants are added to tobacco products to enhance their taste or compensate for variations in tobacco quality and blend. Currently, flavorants are applied to the tobacco portion or the packaging portion of the cigarettes, which results in only small portion of the flavorant being delivered to the user. In addition, the characteristics of flavorants may change after exposure to the high heat of combustion before reaching the user. There is a strong need for a practical and consistent technology to deliver smoke-modifying agents effectively to the user.
A wide variety of fibrous materials have been employed in tobacco smoke filter elements. Cellulose Acetate (xe2x80x9cCAxe2x80x9d) has long been considered the material of choice for this application. However, the choice of materials has been limited because of the need to balance various commercial requirements
A current method for incorporating adsorbent materials in cigarette filters is the physical entrapment of adsorbent particles between CA fibers. The particle size of materials used in such prior art is generally limited in the range of 500 to about 1500 microns in diameter. In order to achieve reasonable product integrity and pressure drop, smaller particles could not be used in this design. In addition, the adsorbents were found to lose activity from exposure to triacetin, a plasticizer used as a binder for the CA fibers.
In order to keep the pressure drop through the filter within acceptable limits, coarse granulated materials in the size of about 10 to about 60 mesh are generally used. A longer shelf life of the adsorbent was achieved, but the efficiency of the filters was limited by the relatively large particle size used. Finer size adsorbent particles with shorter internal diffusive paths and higher effective surface areas cannot be used directly in this configuration due to excessive pressure drop.
Smaller particle size adsorbent/absorbent materials generally have enhanced kinetics of reaction with gas phase components because of their shorter diffusion paths to the interior surface area of such porous materials and the interior body of such absorbent materials. CA fibers currently in use have round or open X or Y cross sections that had carbon dropped in the space, but the cross sections cannot mechanically hold small adsorbent/absorbent particles in place. It was known that employing smaller absorbent particles with shorter diffusion paths can form filters with improved kinetics and capacity for gas phase filtration applications.
It has been found that a fiber with open or semi-open micro cavities is desirable for holding the adsorbent/absorbent material and the flavorant in place. The term xe2x80x9csemi-open cavitiesxe2x80x9d as used herein means cavities that possess openings smaller in dimension than the internal volume of the fiber in which they are formed, and that possess the ability to entrap solid fine particles in their internal volume. The term xe2x80x9copen cavitiesxe2x80x9d means the opening is the same or bigger in dimension than the internal volume of the fiber in which they are formed.
U.S. Pat. No. 5,509,430 which is incorporated by reference in its entirety for all useful purposes including all drawings relates to polymeric bicomponent fibers and to the production of tobacco smoke filters from bicomponent fibers comprising a core of a low cost, high strength, thermoplastic polymer and a bondable sheath of a material. There is a need to develop an improved filter that has better efficiency in selectively removing or reducing undesired components from mainstream cigarette smoke stream.
U.S. Pat. No. 5,191,905 issued to Berger, which is incorporated by reference in its entirety for all useful purposes including all the drawings describes a cigarette filter. The cigarette filter has a filter chip integrally joined to the cigarette section. The filter chip is formed by combining in a bundle, at least one absorptive synthetic fiber selected from the group consisting of (1) graft polymer fibers produced from irradiated polypropylene reacted with vapor phase styrene and containing adsorptive functional groups, (2) activated carbon fibers, (3) charged electret fibers and (4) magnetic plastic fibers and then chopping the combined fibers to a predetermined length. However, Berger does not teach that the fibers (1) have micro-cavities and (2) that the carbon is loaded in the micro-cavities.
To increase the delivery efficiency, efforts have been made to apply flavorants directly to the cigarette filter. However, limitations have rendered their commercialization unpractical. In U.S. Pat. No. 5,356,704, PET fibers that possess axially oriented open grooves spontaneously wettable by water or hexane are used in the outer layer of cigarette filters to enhance the delivery of flavorant in a liquid state. However, the open structure of the grooves limits the capability of the fibers in retaining flavorant components that may be in solid, semi-solid or liquid phase. For example, fibers made of polymers such as polypropylene have open structures, which are impermeable and not wettable by menthol flavorants and therefore do not satisfy the desired end results of flavor delivery.
U.S. Pat. Nos. 5,356,704 and 5,275,859 are assigned on their face to Eastman Chemical Company, and these patents disclose smoke filters. All these patents are incorporated by reference in their entirety for all useful purposes.
The terms xe2x80x9cadsorbentxe2x80x9d or xe2x80x9cabsorbentxe2x80x9d as used herein are defined to mean that the ability of a material to take in or soak up gas components on the surface thereof or to assimilate such components into the body thereof.
Accordingly, an object of the present invention is a cigarette filter comprising shaped micro cavity fibers impregnated with a flavorant that effectively and efficiently modifies the flavor of a stream of smoke during the smoking process.
Another object of the present invention is a cigarette filter comprising shaped fibers having semi-open cavities impregnated with flavorants.
Still another object of the present invention is a fiber filter with flavorants having low resistance to airflow while achieving excellent flavor delivery efficiency.
In accordance with the present invention, a cigarette filter comprises shaped multi-lobal fibers with semi-open cavities loaded with adsorbent particles that include flavorants that release flavors into a smoke stream during the smoking process.